West Nile virus (WNV) emerged from relative obscurity in 1999 when the
first incursion of the virus into North America caused an outbreak of meningoencephalitis
leading to 7 deaths in the New York City area.1 By
2002, human and veterinary surveillance documented geographic spread westward
to the Pacific Coast. In the same year, WNV caused the largest arboviral meningoencephalitis
outbreak ever recorded in North America.2